Engine analysis apparatus

Abstract

Exhaust gas diagnostic apparatus capable of use on both catalytic converter equipped and non-catalytic converter equipped motor vehicles is disclosed. A fast response oxygen analyzer is coupled with means for differentiating the signal output of the oxygen analyzer. In this manner, both the quantity and rate of change of oxygen in the exhaust gas is made available to apparatus included therein for indicating and/or alarming quantity and rate of change values outside preset limits. The apparatus is particularly directed to the detection of an engine misfire condition. The apparatus disclosed permits diagnosing problems without disconnecting the air injector system (if present) or having a port prior to the catalytic converter. As it alarms on transients, it is independent of the steady state oxygen level.

Having thus described our invention, we claim: 
     
       1. Improved engine exhaust gas analysis apparatus comprising: a. means for sampling the exhaust gases including means for generating a first signal indicating the amount of a component present in the exhaust gases;   b. differentiating means connected to said sampling means and including means responsive to said first signal for generating a second signal indicating the rate of change of said first signal with respect to time;   c. means connected to said differentiating means for comparing said second signal to a limit; and,   d. means connected to said comparing means for indicating when said second signal exceeds said limit.   
     
     
       2. Improved engine exhaust gas analysis apparatus as claimed in claim 1 wherein: said component in the exhaust gases is oxygen.   
     
     
       3. Improved engine exhaust gas analysis apparatus as claimed in claim 1 and comprising additionally: means for setting said limit connected to said comparing means.   
     
     
       4. Improved engine exhaust gas analysis apparatus comprising: a. means for detecting a specific component of the exhaust gases;   b. first circuit means connected to said detecting means for producing an output indicating the percent of said component;   c. second circuit means connected to said output of said first circuit means for producing an output indicating the rate-of-change with respect to time of said component;   d. means connected to said output of said second circuit means for comparing the instantaneous value of said output to a limit value; and,   e. alarm means connected to said limit comparing means for indicating an alarm condition when said output of said second circuit means exceeds said limit value.   
     
     
       5. Improved engine exhaust gas analysis apparatus as claimed in claim 4 wherein: said specific component is oxygen.   
     
     
       6. Improved engine exhaust gas analysis apparatus as claimed in claim 4 and comprising additionally: means for setting said limit connected to said limit comparing means.   
     
     
       7. Improved engine exhaust gas analysis apparatus comprising: a. an oxygen sensor adapted to sample exhaust gases of an internal combustion engine:   b. amplifier means connected to said sensor for producing an output indicating the percent of oxygen in said exhaust gases;   c. differentiating means connected to said amplifier means for producing an output indicating the rate of change of said percent of oxygen output with respect to time;   d. means connected to said differentiating means for comparing said rate of change to a limit; and,   e. alarm means connected to said comparing means for signaling when said rate of change is greater than said limit.   
     
     
       8. Improved engine exhaust gas analysis apparatus as claimed in claim 7 and additionally: means for setting said limit connected to said limit comparing means.   
     
     
       9. The method of detecting a lean-roll condition in an internal combustion engine comprising the steps of: a. sampling the exhaust gases from the engine to produce a first signal indicative of the percent of oxygen contained therein;   b. differentiating said first signal to produce a second signal indicative of the time rate of change of said first signal;   c. comparing said second signal to a limit value such that if said second signal exceeds said limit value the engine is in a lean-roll condition; and,   d. activating means for indicating a lean-roll condition when said second signal exceeds said limit value.   
     
     
       10. An improved method of setting the idle mixture adjustment on the carburetor of an internal combustion engine comprising the steps of: a. sampling the exhaust gases from the engine to produce a first signal indicative of the percent of oxygen contained therein;   b. differentiating said first signal to produce a second signal indicative of the time rate of change of said first signal;   c. comparing said second signal to a limit value such that if said second signal exceeds said limit value the engine is in a lean-roll condition;   d. activating alarm means to indicate a lean-roll condition when said second signal exceeds said limit value;   e. adjusting the dwell and timing of the ignition system of the engine to within specifications and to produce the lowest rate of lean-roll alarms;   f. opening the idle mixture screw(s) of the carburetor an amount sufficient to assure a rich mixture condition;   g. closing one idle mixture screw to cause a leaner mixture until a lean-roll condition is alarmed;   h. opening the idle mixture screw adjusted in step (g) an amount to provide a safety margin of richness in the mixture to prevent lean-roll; and,   i. repeating steps (g) and (h) on any other idle mixture screws on the carburetor.